Power stopper

ABSTRACT

Increasing frictional resistance to forward movement is provided by a self-propelled power stopper weight transfer apparatus comprising a four-wheeled vehicle chassis on which there is positioned an elongated mass guide upon which a gear-driven mass of up to ten tons may be moved from a position over a rearward, relatively frictionless means to a forward position over a high friction sled means. A motor power means at the front end of the vehicle chassis not only allows the apparatus to be driven on a highway and acts as a return means during a contest, but also eliminates the need for a separate dead weight on the sled means. Movement of the mass on the mass guide is produced by a direct gear drive connected in the power transmission system. A cab which may be provided on the chassis also adds dead weight. A fifth wheel arrangement on the sled, the attachment of which to the chassis may be controlled from the cab, allows rapid coupling and uncoupling of the apparatus and the sled means for simple, quick and efficient operation.

United States Patent Watkins [15] 3,659,455 51 May 2, 1972 [54] POWERSTOPPER Billy K. Watkins, RR 01, Lovington, Ill. 61937 [22] Filed: Jan.23, 1970 [21] Appl.No.: 5,322

[72] lnventor:

Related [1.8. Application Data [63] Continuation-impart of Ser. No.723,772, Apr. 24,

1968, Pat. No. 3,491,590.

Primary Examiner-Charles A. Ruehl Attorney-Hill, Sherman, Meroni, Gross& Simpson ABSTRACT increasing frictional resistance to forward movementis provided by a self-propelled power stopper weight transfer apparatuscomprising a four-wheeled vehicle chassis on which there is positionedan elongated mass guide upon which a gear-driven mass of up to ten tonsmay be moved from a position over a rearward, relatively frictionlessmeans to a forward position over a high friction sled means. A motorpower means at the front end of the vehicle chassis not only allows theapparatus to be driven on a highway and acts as a return means during acontest, but also eliminates the need for a separate deadweight on thesled means. Movement of the mass on the mass guide is produced by adirect gear drive connected in the power transmission system. A cabwhich may be provided on the chassis also adds dead weight. A fifthwheel arrangement on the sled, the attachment of which to the chassismay be controlled from the cab, allows rapid coupling and uncoupling ofthe apparatus and the sled means for simple, quick and efficientoperation.

14 Claims, 2 Drawing Figures POWER STOPPER BACKGROUND OF THE INVENTIONThis is a continuation-in-part of my co-pending application Ser. No.723,722, filed Apr. 24, 1968, and issued on Jan. 27, 1970, as US. Pat.No. 3,491,590.

This invention generally relates to a measuring and testing apparatus,and more particularly contemplates what may be generally designated as adynamometer for measuring pull. Specifically, my improvement relates toa power weight stopper apparatus which is alternately self-propelled fortransportation between pulling meets and for movement of itself and anattached sled means during a contest.

As described in my co-pending application, the crude and inconsistentmeans for measuring and comparing the pulling energy of tractors wasreplaced by the simple, accurate and re liable power stopper of myinvention.

Thus, my prior invention provided a device for indicating the relativepulling force exerted by a power source comprising a sled adapted to beconnected to and moved by the power source, and a weight transferapparatus having a front portion supported by a ground engaging sled anda rear portion supported by means which allow relatively friction freemovement of the apparatus. The weight transfer apparatus embodies anelongated weight mass guide extending along the weight transferapparatus and supporting thereon a relatively movable mass which may bemoved therealong a distance proportional to the distance through whichthe device is pulled by a mass moving means. As the weight moves from aposition over the rearward relatively friction-free ground engagingmeans to a position where its center of gravity is near the highfriction ground engaging means at the forward end the friction force onthe sled increases thereby slowing or actually stopping the pullingapparatus. In practice an additional dead weight almost always waspresent on the sled to provide an initial stability and friction force.Upon the completion of a pull, which may be as much as 200 to 300 feetor more, depending on the course, a separate tractor or pullingapparatus attached itself to the power stopper and the sled to returnthem to their initial starting positions for the next contestant. Tomove the apparatus cross country from one tractor pulling meet toanother required that the device be carefully loaded on anothertransporting means, moved cross country and then be carefully unloaded.

SUMMARY OF THE INVENTION The instant invention is directed toimprovements on my basic invention and thus it will be understood thatthis invention carries forward my prior invention and adds thereto afurther invention. Thus, I have discovered that by adding a motor powermeans and steerable front wheels to the forward end of an apparatusaccording to my prior invention I can not only propel the apparatus overroads and highways in substantially the same condition as it is whenused during a contest to thereby eliminate a separate hauling vehiclewith the accompanying loading and unloading time, but in addition, themotor power means connected through a transmission system with the rearwheels would allow my apparatus to be self propelled and return itselfto its initial starting position after each contestant has finishedthereby eliminating the personnel and equipment which ordinarily had tostand-by to accomplish the same result.

Another advantageous result accomplished by my present invention is thatthe placement of the motor power means, front wheel means and cabstructure at the forward end of my apparatus provides a large enoughweight so that the heretofore required dead weight means on the sledsuch as illustrated by the tractor in my prior application, may now beeliminated.

Having provided a power transmission means driving the apparatus throughthe rear wheel means, I have found it advantageous to employ a geardrive weight mass moving embodiment of my prior invention. It will beunderstood that the gear drive weight mass moving concept set forthherein was within the contemplation of my prior invention and does notform a part of the present invention except insofar as it relates to thenew and advantageous combination of this invention.

A specific embodiment of my invention herein includes a stable movablechassis or transporting under carriage having relatively friction freefront and rear wheel means. Each wheel means may comprise a pair ofwheels on an axle. The front wheel means must be steerable to allowmovement of the apparatus over roads and highways. A cab mounted on theforward end of the chassis contains a seat and steering wheel means. Amain support or mass guide extends from behind the cab along the chassispast the rear wheel means. A weight receiving trolley which may beshorter than it is wide rides on the main support and is movedtherealong in direct relationship to the movement of the entireapparatus by a suitable weight moving means which may advantageouslytake the form of a rotatable geared drive shaft connected to and drivenby the rear wheels of the transporting under carriage. Thus, as the rearwheel means on the under carriage turn during the forward movement ofthe apparatus, they drive the rotatable geared drive shaft. Since it isimportant that the rear wheels rotate easily during the movement of theapparatus over the pulling course, the drive system for the weighttrolley may be geared down.

A motive power source which may be positioned at the front end under thecab is connected to the rear wheel means by a suitable motive powertransmission system so that when the weight drive system is disconnectedfrom the rear wheels the motive power drive system may be connectedthereto to move the apparatus to its initial starting position and alsoto drive the apparatus over roads and highways between various locationsof use.

Another important feature of my invention is the provision of a fifthwheel means on the sled along with inclined positioning blocks so thatthe weight transfer apparatus may be easily moved onto and off of theground engaging sled. Thus, when the weight transfer apparatus is to bemoved onto the sled the front wheels move up the positioning blocks andoff of the end to position the front end of the weight transferapparatus on the fifth wheel and engage a kingpin on the fifth wheelwith the underside of the front end of the weight transfer apparatus.Provision of the fifth wheel allows an articulated connection betweenthe sled and the weight transfer apparatus so that the combination maysnake over the source of pull. When it is desired to remove the weighttransfer apparatus from the sled the motive power source is engaged withthe rear wheels and is pulled up over the end of the positioning blockand of off the sled. A chain connected to the forward end of the weighttransfer apparatus and the rear end of the sled allows the weighttransfer apparatus under its motive power to pull the sled back with itto the exact starting line and then the weight transfer apparatus isdriven back onto the sled for the next contestant.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view withparts in cross-section of an improved apparatus according to myinvention and,

FIG. 2 is a cross-sectional view taken along the lines lI-ll in FIG. Ishowing the relation of the weight to the chassis.

DESCRIPTION OF THE PREFERRED EMBODIMENT There is shown in FIG. 1 a selfpropellable means in the form of a power stopper weight transferapparatus generally indicated at 10 mounted in position on a frictionalresistance means such as shown by the sled 12 which engages the ground14. The sled 12 has a hitch means 16 at its forward end to which therewill be attached the device whose power output is to be measured by thecombination of the weight transfer apparatus and the sled 12.

The self propellable means 10 includes an elongated chassis orunder-carriage 20 which is supported at its first or rearward end 20a bya first wheel means 22 and which is supported at its second or forwardend 20b by a second wheel means 24. A main support means or mass guide30 may be mounted on or integral with the chassis 20. A weight mass 40is supported by said mass guide 30 for movement therealong.

A motive power means 50 is supported by the chassis 20 at its forwardend. A cab 60 may be mounted over said motive power means on the frontend of the chassis 20b. The motive power means 50 may be of aconventional internal combustion design although any suitable means iscontemplated. Likewise, the cab 60 may be of a conventional design andincludes therein a steering mechanism generally indicated at 62 whichallows steering of the front wheel means 24 from the cab 60. In thisform the weight transfer apparatus 10 may be driven by the motive powermeans 50 over highways or to return itself to a starting position afterhaving been pulled by a contestant in a tractor pulling contest. Anattachment means 80 allows the forward end of the weight transferapparatus 10 to be positively and pivotally attached to the groundengaging sled 12 so that when the apparatus whose force is to bemeasured is attached to the sled at 16 and pulls the sled l2 and theconnected weight transfer apparatus 10 forward, the weight means 40 willbe moved forwardly by suitable weight movement means generally indicatedat 100 through a distance which is proportional to the distance that theweight transfer apparatus and attached sled are moved. The measurementof the distance through which each competing tractor moves the weighttransfer apparatus or the time in which each competing tractor moves theapparatus over a course of a fixed distance will determine the relativepower of the competing tractors.

According to my instant invention the addition of the motive power means50 to the forward end 20b of the chassis 20 and its connection to thefirst wheel means 22 with a first drive shaft means generally indicatedat 52 allows the self propellable weight transfer apparatus 10 to propelitself as a normal vehicle over highways and allows it to return itselffrom its final pull position to its initial starting position after eachpull. In addition, the weight of the motive power means 50, the secondwheel means 24, the cab means 60 and the attachment means 80 provides adead weight that is transferred to the sled 12 and replaces the extradead weight heretofore required.

The first wheel means 22 may advantageously take the form as shown inFIG. 2 of pairs of wheels mounted on opposite sides of an axle structurehaving a single speed differential means 27.

A first drive shaft 52 is connected at its rearward end to thedifferential means 27 and has a first gear means generally indicated at28 connected to its forward end. A second gear means generally indicatedat 54 in turn is connected between the first gear means 28 and themotive power source 50. With this arrangement the first wheel means 22may be driven by the power source 50 to move the apparatus 10 forward orrearward on its wheel means 22, 24 by power transmitted through anengaged second gear means 54, a disengaged first gear means 28 and thefirst drive shaft 52. The second gear means 54 may be of a structure andfunction much like a conventional automotive transmission to allow thetransmission of power from the motive power means 50 at different ratesof speed. Accordingly, this structure will be understood by thoseskilled in that art and need not be set forth in detail.

During movement of the self propellable means 10 when it is mounted onthe sled 12 the rotationof the wheel means 22 is transmitted by thedifferential means 27 through the first drive shaft 52, through anengaged first gear means 28 to a weight movement means 100 whereby theweight 40 moves in response to movement of the apparatus. The secondgear means 54 will at this time be disengaged from the first gear means28. It will be understood by those skilled in the art that theengagement and disengagement of the first and second gear means may beby conventional means such as clutches which are operable in aconventional manner from the cab. In the embodiment shown I haveincluded a schematically illustrated clutch means 55 in the second gearmeans 54 and provide a clutch means 119 in the weight movement means100.

The first gear means 28 as schematically shown in FIG. 1 may transmitpower to the weight movement means through a first chain drive means 140including a sprocket 141 mounted on the first drive shaft 52, a sprocket142 mounted on a second drive shaft 104 and chain 143 thereabout. Inthis arrangement I have found a 2:1 sprocket ratio and a number 60roller chain of a pitch to provide excellent results.

Inasmuch as the first wheel means 22 has a gear means to allow it to bedriven by the motive power means 50 l have found it advantageous toprovide a direct drive geared weight movement drive system 100. In thisgeared weight drive system 100 the rotary power of the wheels istransmitted through the differential 27 to the first gear means 28,thence through the power output gear means 140, to the second driveshaft 104, through a clutch means 119, through a third gear means 106,through a third drive shaft 105 and through a second chain drive means120 to a fourth drive shaft which in turn moves the weight 40. Thefourth drive shaft 110 may advantageously be centrally positioned on thechassis 20 and extended through an opening 42 in a central portion 400of the weight means 40 that depends between the guide support means 30.A suitable mating gear engaging means 42a is affixed to the interior ofthe opening 42 and engages the threaded shaft 110 so that rotation ofthe shaft 110 will move the weight means 40 along the supporting massguide 30. Rotation of the shaft 110 in a first direction moves the mass40 forward while rotation in a second direction moves the mass 40rearwardly.

The third gear means 106- allows a final speed control of the Acme gearshaft 110 and may include various gear ratios to provide a generallyequal course of travel regardless of the class of tractor pulling theapparatus. An excellent range is provided by a four speed gear meanshaving ratios of 1:1, .8l25:l, 6.25:], and .4,063:1.The third gear shiftmeans may be directly on the gear box since it will be changed only fordifferent classes. This also has the advantage that the confidence ofthe participants in the integrity of the apparatus is increased when allvariable controls and their actuators are clearly displayed. Since thechain drive means 140 and are clearly visible and when the differential27 is of a single speed type no change in ratios can be made hence thethird gear means 106 may be the only effectively hidden" variable andthus its control should be visible. A differential 27 of a multi-speedtype may in some respects provide some of the advantages of the thirdgear means 106, however, in view of the use of the differential 27 forcross country driving as well I have found that arrangement not entirelysatisfactory. Moreover, with the third gear means in position as shownthe weight return is facilitated as will hereinafter be made clear.

To reduce the friction between the guide 30 and the mass 40 there may beprovided suitable wheel means 44 between the guide 30 and the weightmass 40. When the weight mass guide 30 takes the form of I beams such asshown for example in FIG. 2, further wheeled guide means such as shownat 46 may be provided below the upper flange to space the mass and tolock the mass in place against upward movement. The relativelyfrictionless guide means 44, 46 may be spaced along the length of theweight 40 to prevent binding of the weight during its movement along theguide means 30. The guide means 30 may have its upward surfaceconfigured in an upwardly pointed shape as shown and the wheels 44 maybe of mating engagement therewith to increase lateral stability of theweight means 40 on the guide 30. In addition suitable guide rail supportmeans 32 may be provided to connect the guide 30 to the chassis means20.

As heretofore stated, forward movement of the'mass 40 from a position asshown in solid lines at 40 to a forward position such as shown forexample at 40' in dotted lines results when the wheel means 22 rotate inresponse to forward movement of the apparatus and the rotationalmovement is transmitted through the weight movement drive system 100 toturn the shaft 110 in a first direction.

Return of the weight mass from a position such as shown at 40 to theinitial starting position illustrated at 40 is easily effected throughthe combination of my invention by the provision of a power take-offmeans 56 transmitting motive power from the source 50 to the fourthshaft means 110. The power take-off means 56 includes a take-off couple57 on the second gear means 54 whereby power from the source 50 may betransmitted through fifth drive shaft 58, through a third chain drivemeans 130 to the third drive shaft means 105 from where it will betransmitted by the second chain drive 120 to turn the drive shaft 110 inthe second direction and move the weight 40 rearwardly back to itsinitial starting position. It should be noted that the return drivemeans 56 does not go through the first or third gear means 28 and 106respectively so that the rotational speed of the fourth drive shaft 110will be greatly increased. By this construction the weight 40 may bemoved along the guide 30 irrespective of the movement of the weighttransfer apparatus 10. Suitable safety means may be provided to insurethat during a pull the power return means 56 is disengaged and movementof the weight 40 is possible only through the weight movement drivesystem 100.

The engagement and disengagement of the various gears in the first gearmeans 28 may also be advantageously controlled by remote control meansconveniently located in the operators cab 60.

It is another advantageous feature of my invention that the weighttransfer apparatus 10 may be quickly, simply and securely mounted on thesled 12 by an attachment means 80 which includes an adjustable support90, a fifth wheel 82, a pair of inclined wedge shaped blocks 84, akingpin means 86 and a remote controlled lock means 88. The fifth wheel82, the kingpin means 86 and lock means 88 may be of a designconventional with tractor trailers and thus will be understood by thoseskilled in the art. The connector means 80 is positioned behind thefront wheels 24 and as shown may be very nearly directly below theforwardmost position of the weight 40. A support structure 90 attachedbelow and between the chassis may include rows of holes 92 generallyparallel to the chassis 20 and spaced an inch or two apart to allowupward and downward adjustment of the support and the attached chassis20. This changes the angle of inclination of the guide and while thiswill have no effect on the movement of the weight it will allow ease inbalancing of the apparatus.

The support 90 has a bottom 94 on which the kingpin 86 of suitableconfiguration is centrally mounted so that it depends downwardly adistance adequate to allow engagement with the fifth wheel means.

It will be understood by those skilled in the art that suitable bearingmeans 108 and universal joints 109 may be provided where necessary onthe drive shafts and gear means of my in vention.

To mount the weight transfer apparatus 10 on the sled 12 the secondwheel means 24 are driven up an inclined portion 120 of the sled, upalong a pair of lifting blocks 84 spaced on opposite sides of the fifthwheel 82 until they pass over an upward forward edge 84a of the liftingblock 84. When the second wheel means 24 pass over the edge 84a thekingpin means 86 engages the fifth wheel means 82 and provides the soleconnection between the apparatus 10 and the sled 12. At this point thewheel means 24 are suspended in the air above the sled l2 and the groundsurface 14. In this position the entire weight of the weight transferapparatus is applied directly to the fifth wheel 82 and the sled 12.

When it is desired to remove the weight transfer apparatus 10 from thesled 12 the ground engaging first wheel means 22 are driven by themotive power drive system and the remote control lock 88 released sothat the kingpin means 86 may move out of the fifth wheel 82. Uponrearward movement of the apparatus 10 the wheel means 24 again movesup-and over the edge 84a of the lifting block 84 and rolls down and offthe block 84. A chain means connected between the front end of theweight transfer apparatus 10 and the rear end of the sled 12 will allowthe weight transfer apparatus 10 moving under the power of the motivesystem to drag the sled 12 back to the starting position at which pointthe weight transfer apparatus 10 is again moved onto the sled 12 asheretofore described in preparation'for the next pull. it is importantto note that by adding to the front end of the weight transfer apparatus10 the dead weight provided by the motive power means 50, the cab 60 andwheel means 24, for example, the extra dead weight previously requiredfor the sled 12 may be eliminated. Also, this weight is automaticallyremoved after each pull thereby making possible the return movement ofthe sled by a means of considerably less power than is necessary where adead weight remains on the sled 12.

From the above noted description of the preferred embodiment of myinvention it will be understood that l have provided a new and improvedpower stopper weight transfer apparatus that is not only very accuratebut is simple and convenient to operate. Thus, no extra personnel orequipment is needed to move the weight transfer apparatus betweengeographically separated meets. The weight transfer apparatus may bedriven under its own motive power system 50 over roads and highways justas an ordinary vehicle and loading and unloading of the apparatustogether with the necessary time and personnel is eliminated. Inaddition to these great advantages it is now possible with my inventionto also eliminate the equipment and personnel 'that heretofore have beenrequired to stand-by during a contest to return the power stopperapparatus from its final position to an initial starting position, Thisis of considerable advantage because the equipment previously requiredto return the apparatus had to be of considerable power inasmuch as thesled of prior art devices carried a heavy dead weight tractor and thuspresented considerable frictional resistance to movement.

With the apparatus of my invention herein disclosed a single operatormay perform the same functions in considerably less time than itpreviously took three or four personnel and two additional pieces ofexpensive equipment.

Although minor modifications might be suggested by those versed in theart such as for example the provision of equivalent weight movementdrive systems or specific equivalent gear means, it should be understoodthat I wish to embody within the scope of the patent warranted hereonall such modifications as reasonably and properly come within the scopeof my contribution to the art as defined by the claims.

I claim as my invention:

1. An apparatus movable over a ground means for measuring or comparingthe pulling ability of a tractive power means comprising a frictionalresistance means adapted to engage said ground means and a meansdetachably connected to said frictional resistance means for varying thefrictional resistance to movement of the apparatus in relation to thedistance through which the apparatus is moved over the ground means,said means for varying the frictional resistance having a first portionand a second portion, said first portion being adapted to engage saidground means and said second portion being removably mounted on saidfrictional resistance means, said means for varying the frictionalresistance including a motive power source whereby said means varyingthe frictional resistance is self propellable when detached from saidfrictional resistance means.

2. An apparatus according to claim 1 wherein said frictional resistancemeans is a sled means having a large flat surface adapted to lie in flatengagement with the ground means.

3. An apparatus according to claim 2 wherein said self propellable meansfor varying the frictional resistance includes a weight transfer meanswhich increases the weight applied to the sled means to thereby increaseits frictional resistance, said self propellable means being removablefrom said sled to return said apparatus to a starting position.

4. An apparatus according to claim 2 wherein said sled means has a firstend and a second end, said first end being adapted to be attached to thetractive power means whose pull is to be measured or compared, and saidsecond end having an attachment means thereon allowing ready attachmentand detachment of said self propellable means. v

5. An apparatus according to claim 4 wherein said attachment meansincludes a fifth wheel means on said sled means and a kingpin meansconnectible between said self propellable means and said fifth wheel,said attachment means further including an inclined wedge-shaped liftingblock means positioned so that said self propellable means may be driventhereon to be locked in position on said sled.

6. An apparatus according to claim 4 including a remote controlleddetachment means connected with said attachment means for remotelydetaching said self propellable means from said sled.

7. An apparatus according to claim 4 wherein said self propellable meansincludes an operators cab at said second portion over said motive powersource, said cab having control means for said motive power source and ameans to steer wheel means at said second portion and wherein saidmotive power source, said wheel means and said cab provide a dead weightacting on said sled.

8. An apparatus according to claim 1 wherein said self propellable meanshas a first wheel means at said first portion and a second wheel meansat said second portion, said second wheel means being supported on saidfrictional resistance means during movement of said apparatus in a firstdirection, and said second wheel means being movable off of saidfrictional resistance means and engaging the ground when said apparatusis moved in a second, generally opposite direction.

9. An apparatus according to claim 8 wherein said first wheel meansengage the ground means during all movement of said apparatus, saidmotive powersource being selectively connectible in driving relationshipto said first wheel means to propel said carriage under its own power insaid second direction.

10. An apparatus according to claim 8 wherein said second wheel means isremovably mounted on said frictional resistance means by an attachmentmeans, said attachment means including a fifth wheel means on saidfrictional resistance means.

11. An apparatus according to claim 8 wherein said second wheel means issteerable through a steering means mounted on said self propellablemeans, said second wheel means being adapted to be mounted on and oversaid frictional resistance means, said self propellable means includinga frame means, said motive power source being mounted on said framemeans in the area of said second portion of said self propellable means;a motive power drive system connecting said motive power source withsaid first wheel means; said motive power drive system comprising aclutch means allowing engagement and disengagement of said power sourcewith said first wheel means whereby said first wheel means may bedisengaged from said power source during movement of said apparatus insaid first direction and may be engaged with said power source when saidapparatus is moved in said second direction.

12. An apparatus according to claim 11 wherein said self propellablemeans has a weight means movable between an initial position where itsweight is transferred mainly to said first wheel means and a secondposition where its weight is transferred mainly to said frictionalresistance means, a weight movement means disengageably connected tosaid first wheel means whereby when said apparatus is moved in saidfirst direction said first wheel means moves said weight by means ofsaid weight movement means.

13. An apparatus according to claim 12 wherein said weight movementmeans includes a differential gear means for conveying rotary movementof said first wheel means to a first drive shaft connecting saiddifierential gear means with a first gear means, said first gear meanstransmitting said rotary movement to a second drive shaft and throughsaid clutch means to a third gear means, said third gear means providinga rotary movement speed control means, said rotary movement beingtransmitted from said third gear means through a third drive shaft to afourth gear drive shaft which rotates to move said weight.

14. An apparatus according to claim 11 wherein said first portion ofsaid self propellable means is a relatively friction free groundengaging means, said self propellable means having a weight meansmovable from an initial position where its weight is transferred mainlyto said relatively friction free ground engaging first portion towardand to a position where its weight is transferred mainly to saidfrictional resistance means, said movement of said weight means being indirect relation to the movement of said apparatus whereby saidfrictional resistance to movement of said apparatus varies in relationto the distance through which said apparatus has been moved.

1. An apparatus movable over a ground means for measuring or comparing the pulling ability of a tractive power means comprising a frictional resistance means adapted to engage said ground means and a means detachably connected to said frictional resistance means for varying the frictional resistance to movement of the apparatus in relation to the distance through which the apparatus is moved over the ground means, said means for varying the frictional resistance having a first portion and a second portion, said first portion being adapted to engage said ground means and said second portion being removably mounted on said frictional resistance means, said means for varying the frictional resistance including a motive power source whereby said means varying the frictional resistance is self propellable when detached from said frictional resistance means.
 2. An apparatus according to claim 1 wherein said frictional resistance means is a sled means having a large flat surface adapted to lie in flat engagement with the ground means.
 3. An apparatus according to claim 2 wherein said self propellable means for varying the frictional resistance includes a weight transfer means which increases the weight applied to the sled means to thereby increase its frictional resistance, said self propellable means being removable from said sled to return said apparatus to a starting position.
 4. An apparatus according to claim 2 wherein said sled means has a first end and a second end, said first end being adapted to be attached to the tractive power means whose pull is to be measured or compared, and said second end having an attachment means thereon allowing ready attachment and detachment of said self propellable means.
 5. An apparatus according to claim 4 wherein said attachment means includes a fifth wheel means on said sled means and a kingpin means connectible between said self propellable means and said fifth wheel, said attachment means further including an inclined wedge-shaped lifting block means positioned so that said self propellable means may be driven thereon to be locked in position on said sled.
 6. An apparatus according to claim 4 including a remote controlled detachment means connected with said attachment means for remotely detaching said self propellable means from said sled.
 7. An apparatus according to claim 4 wherein said self propellable means includes an operators cab at said second portion over said motive power source, said cab having control means for said motive power source and a means to steer wheel means at said second portion and wherein said motive power source, said wheeL means and said cab provide a dead weight acting on said sled.
 8. An apparatus according to claim 1 wherein said self propellable means has a first wheel means at said first portion and a second wheel means at said second portion, said second wheel means being supported on said frictional resistance means during movement of said apparatus in a first direction, and said second wheel means being movable off of said frictional resistance means and engaging the ground when said apparatus is moved in a second, generally opposite direction.
 9. An apparatus according to claim 8 wherein said first wheel means engage the ground means during all movement of said apparatus, said motive power source being selectively connectible in driving relationship to said first wheel means to propel said carriage under its own power in said second direction.
 10. An apparatus according to claim 8 wherein said second wheel means is removably mounted on said frictional resistance means by an attachment means, said attachment means including a fifth wheel means on said frictional resistance means.
 11. An apparatus according to claim 8 wherein said second wheel means is steerable through a steering means mounted on said self propellable means, said second wheel means being adapted to be mounted on and over said frictional resistance means, said self propellable means including a frame means, said motive power source being mounted on said frame means in the area of said second portion of said self propellable means; a motive power drive system connecting said motive power source with said first wheel means; said motive power drive system comprising a clutch means allowing engagement and disengagement of said power source with said first wheel means whereby said first wheel means may be disengaged from said power source during movement of said apparatus in said first direction and may be engaged with said power source when said apparatus is moved in said second direction.
 12. An apparatus according to claim 11 wherein said self propellable means has a weight means movable between an initial position where its weight is transferred mainly to said first wheel means and a second position where its weight is transferred mainly to said frictional resistance means, a weight movement means disengageably connected to said first wheel means whereby when said apparatus is moved in said first direction said first wheel means moves said weight by means of said weight movement means.
 13. An apparatus according to claim 12 wherein said weight movement means includes a differential gear means for conveying rotary movement of said first wheel means to a first drive shaft connecting said differential gear means with a first gear means, said first gear means transmitting said rotary movement to a second drive shaft and through said clutch means to a third gear means, said third gear means providing a rotary movement speed control means, said rotary movement being transmitted from said third gear means through a third drive shaft to a fourth gear drive shaft which rotates to move said weight.
 14. An apparatus according to claim 11 wherein said first portion of said self propellable means is a relatively friction free ground engaging means, said self propellable means having a weight means movable from an initial position where its weight is transferred mainly to said relatively friction free ground engaging first portion toward and to a position where its weight is transferred mainly to said frictional resistance means, said movement of said weight means being in direct relation to the movement of said apparatus whereby said frictional resistance to movement of said apparatus varies in relation to the distance through which said apparatus has been moved. 